Erosion control system and method of manufacturing same

ABSTRACT

An erosion control system is provided which generally includes a flexible composite blanket or matting including a core layer formed of rice straw. In addition, the present invention provides a green pigmented rice straw fiber blanket and methods for making same.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.10/894,641 filed on Jul. 20, 2004 which claims the benefit of U.S.provisional patent application No. 60/489,256 filed on Jul. 22, 2003 andwhich is a continuation-in-part of U.S. patent application Ser. No.10/072,149 filed on Feb. 6, 2002, which claims the benefit of U.S.provisional patent application No. 60/266,782 filed on Feb. 6, 2001, theentire disclosure of each of which being incorporated herein by thisreference.

BACKGROUND OF THE INVENTION

The present invention generally relates to erosion control, and morespecifically relates to temporary or permanent turf reinforcement andsoil retention matting or blankets.

Erosion control is an essential environmental consideration when newslope embankments and channels are created, for example duringconstruction of buildings and drainage systems. Traditionally, newlyconstructed channels have been lined with concrete or rock to provide ahard, armor-like channel lining. Alternatively, the development of rootreinforcement systems is relied upon to control erosion. Thus, methodshave been developed for stabilizing soil on channel linings and othererosion prone surfaces by encouraging the growth of native or introducedvegetation along the surface. Ideally, a mature root system within thesloped surface functions to bond together the channel surface andinhibit soil loss during rains and other stresses.

However, embankment and channel surfaces often require reinforcement,particularly during the pre-vegetated stage and early stages of plantgrowth, to prevent loss of soil, seeds, seedlings and other small plantswhen the soil is in an unstable state.

Various reinforcement systems have been developed. For example, U.S.Pat. No. 5,849,645 to Lancaster, which is incorporated herein by thisspecific reference, discloses reinforced composite matting including afiber matrix secured together by an arrangement of multiple nettings.The nettings form a series of alternating troughs and ridges, frombetween one eight an inch in height to one inch in height, along thematting. This three dimensional, “cuspated” aspect of the Lancastermatting is designed to trap mulch, sediment, and plant seeds in thetroughs during early stages of plant growth. According to Lancaster, thetrapped soil and other debris provide a growing medium for sproutingplants. Although the Lancaster patent recognizes the problems associatedwith erosion on new channel surfaces, the matting system disclosed doesnot address other problems, for example, high shear stress on thematting, particularly during long duration, high velocity water flowduring the critical pre-vegetated stage. Furthermore, the Lancastersystem requires that the matting be placed in a specific alignment withrespect to channel flow. More particularly, Lancaster discloses that inorder for the matting to trap sediment between the troughs and ridges,the matting is to be installed such that the troughs and ridges areperpendicular to the intended direction of channel flow. Thisrequirement poses potential installation problems and setbacks.

Conventional prior art erosion control blankets have utilized wheatstraw, coconut fiber, chopped or crimped synthetic polypropylene fibersor a blend thereof. Wheat straw, in particular, has long been anindustry standard. Erosion control blankets made primarily of wheatstraw suffer a number of disadvantages. For example, the naturaldecomposition process of wheat straw tends to extract nitrogen and otherplant nutrients from the soil surface to which the straw is applied,thus detrimentally affecting soil fertility. Plants and seedlingsgrowing from the surface and through the wheat straw-based covering doesnot promote the optimal growth of plant roots, thus delaying orhindering the goal of soil stability. To counteract this effect,fertilizers and other such additives are oftentimes incorporated intothe blanket material in an effort to maintain or boost soil fertilityduring the early stages of plant growth.

Traditional wheat straw erosion control blankets are often relied uponfor covering bare soil around a newly constructed home or other buildingprior to the establishment of landscaping. Unfortunately, thesetraditional erosion control blankets are aesthetically unappealing andare usually removed and discarded prior to mature landscaping beingestablished, thus leaving the property in an unprotected state open topotential discharge of pollutants, which, in some jurisdictions, is aviolation of state water quality regulations.

It will be appreciated by those of skill in the art, that the objectivesof the present invention, for example, greater soil stability andestablishment of foliage and a healthy root system, are essentially thesame objectives to which conventional erosion control blankets havegenerally been directed. However, conventional erosion control blanketdesigns have been inadequate, for example, during high velocity, longterm, sustained water flow conditions, and even more so when saidblankets have been installed to a non-vegetated, bare or seeded soilsurface.

There is still a need for an effective, aesthetically appealing erosioncontrol product and method that will address at least some, andpreferably all of the problems of prior art products and techniques.

The present invention provides a more effective, more technicallyadvanced system for controlling soil loss erosion on channel andembankment surfaces, particularly during the critical pre-vegetationstage and in areas exposed to severe conditions of continuous, extended,high velocity water flows, and high shear stress erosion.

Another well known, related problem is a lack of an effective techniqueand/or product useful for covering and protecting newly developed land,for example, adjacent nearby newly constructed homes and the like.Traditional wheat straw environmental control blankets are highlyunattractive to new homeowners and are therefore usually removed anddiscarded prior to the establishment of mature landscaping, This leavesthe land in an unprotected state. Unfortunately, this practice is notconsidered environmentally acceptable, and is in some jurisdictionsunlawful, in that it potentially opens adjacent properties to receivingrunoff and potential discharge of pollutants.

The present invention also provides cleaner, substantially naturallyweed free, more aesthetically appealing, more landscape friendly, moreeffective erosion control systems, relative to conventional erosioncontrol products, and methods for protecting surfaces on newly developedland, for example, adjacent homes and office buildings, prior to andduring the establishment of landscaping.

SUMMARY OF THE INVENTION

Accordingly, an erosion control system is provided, which generallycomprises a flexible matting adapted to be secured to or placed on asurface, for example a substantially non-vegetated surface.

In one particularly useful embodiment of the invention, the systemcomprises a erosion control matting structured to substantially preventsoil loss on a substantially unvegetated and/or sloped surface, evenwhen the matting is exposed to high velocity and/or long durationhydraulic events.

More particularly, this embodiment of the invention generally comprisesa core layer formed of a fiber matrix comprising randomly orientedfibers, and a upper layer, bonded or secured to the core layer, whereinthe core layer and the upper layer define a substantially flat uppersurface. A flat upper surface is more specifically defined herein as asurface being without substantial three-dimensional features such ascuspations, pockets, ridges, or the like. Advantageously, the matting ofthis embodiment of the present invention has a substantially higher massunit density in comparison to conventional erosion control mats.Specifically, the matting has a mass unit density of at least about 0.5pounds per square yard and more preferably at least about 0.7 pounds persquare yard (dry weight).

In one embodiment of the invention, the fiber matrix core preferablycomprises a material selected from the group consisting of coconutfibers, flax fiber, polypropylene fibers, for example choppedpolypropylene fibers, and combinations thereof.

The upper surface of the matting, in accordance with one embodiment ofthe present invention, preferably has a Manning's “N” value of roughnessof less than about 0.044, and preferably has a roughness value of about0.026 or less.

Advantageously, it has been found that during a storm event, the presentsystem more effectively resists high shear stresses, such that highvelocity liquid flow passes over the upper surface of the mattingwithout substantially removing any of the soil beneath the matting. Itis noted and will be appreciated by those of skill in the art, thatconventional matting systems have typically been designed withsubstantial three dimensional features, primarily as a means of trappingsoil during water flow over the surface of the matting. Although notwishing to be bound by any particular theory of operation, it isbelieved that the relatively flatter structure of the matting inaccordance with the present invention contributes to the system beingable to withstand higher flow velocities, by decreasing the high shearstress forces created, for example, by an increasing water depth flowingover a relatively rough surface.

In another particularly advantageous embodiment of the invention, anerosion control system is provided, comprising a flexible mattingeffective in controlling erosion and structured to be secured or placedon a surface prone to erosion, the matting including a substantiallyuniform core layer formed of rice straw fibers, for example, fibers ofCalifornia Rice Straw.

For example, in an especially advantageous embodiment of the presentinvention, an erosion control system is provided which generallycomprises a flexible matting effective to control erosion, wherein thematting includes a core layer that is comprised substantially entirelyof rice straw fibers, and the matting has a substantially higher aerialdensity relative to an identical flexible matting not formed of ricestraw fibers.

In one embodiment of the invention, the matting comprises a core layermade substantially entirely of rice straw fibers. This embodiment of theinvention is particularly beneficial to providing a substantiallysuperior environment (relative to conventional erosion control matting)that enhances germination and growth of plants without robbing theplants of beneficial nutrients.

The present invention also provides methods for processing rice straw,and methods for manufacturing rice straw blankets. It is noted thatprior to the development of the present inventive methods, bulk bales ofrice straw have been extremely difficult, if not impossible, to processto process using standard erosion control blanket manufacturingequipment.

The methods of the present invention include the steps of pulling ricestraw fibers, for example from a bulk bale of rice straw, using amechanism structured to separate and/or pull fibers of rice straw fromthe bale to achieve long, thin, more easily manageable rice strawfibers. More particularly, the methods comprise the step of utilizing aplurality of high speed rotating blades to contact and draw fibers fromthe bale.

The method may further include the step of discharging the rice strawfibers onto high speed exit conveyors. The method of the presentinvention effectively transforms the bulk rice straw bale into asubstantially continuous, even fiber pile that is capable of being usedon a surface for controlling erosion on the surface. The even fiber pileis of a form that that can be readily processed and digested byconventional blanket manufacturing material handling systems.

The rice straw fiber pile may be mechanically stitched, bonded orotherwise reinforced to form a blanket. A reinforcement element such asa netting material may be located on at least one of an upper surface ofthe core layer and the bottom surface of the core layer. In other words,a reinforcement element may be stitched or bonded to at least one of themajor surfaces of the core layer. Stitching of the matting may beaccomplished by any suitable means, for example but not limited to bystitching the core layer at specific intervals, for example, but notlimited to between about one inch and about two inches on centers toensure substantial uniformity of the matting. Preferably, stitching issewn with monofilament thread or twisted multifilament thread of aminimum of about 1,000 denier or greater.

In a particularly advantageous embodiment of the invention, a method forcontrolling erosion is provided, including the steps of applying debatedrice straw fibers in a substantially continuous, even layer onto asurface prone to erosion and allowing the rice straw fibers to remain onthe surface during growth of seedlings and mature plants.

In another especially advantageous embodiment of the invention, apigmented erosion control blanket is provided. It has been discoveredthat rice straw can be successfully pigmented, in accordance withmethods of the present invention to achieve an aesthetically pleasing,high quality erosion control matting. For example, the present inventionprovides a green pigmented erosion control matting that providesconstruction developers an aesthetically pleasing ground cover forapplication around newly constructed homes.

It is noted, and will be appreciated and known by those of skill in theart, that all trials and attempts to dye natural erosion control fiberblankets, for example blankets of wheat straw, have been largelyunsuccessful.

The present invention therefore provides a pigmented erosion controlblanket, for example a green pigmented erosion control blanket. Morespecifically, the present invention provides a pigmented rice strawerosion control blanket. This embodiment of the invention is especiallyuseful as a visually appealing, substantially weed free ground coverthat aids in preventing runoff of soil, for example on newly developedland.

In a related aspect of the invention, a method of dyeing or pigmentingrice straw is provided. For example, after the stitching process of therice straw mat or blanket generally described hereinabove, the ricestraw mat is then passed under a low pressure spray bar which applies aninventive pigment composition.

A pigment composition in accordance with the present invention, fortinting or coloring rice straw fibers, generally comprises an aqueouspigmentation composition comprising an aqueous mixture of a pigmentcomponent, a binder component and an effective amount of a wettingagent, or surfactant. For example, in accordance with one embodiment ofthe present invention, a pigment solution concentrate is provided thatcan be combined with a diluent such as water prior to being applied torice straw fibers.

The pigment solution concentrate may comprise about one part pigmentcomponent, for example a latex polymer dispersion having a desiredcolor, for example but not limited to pigment green, and about one partbinder component, for example a polymer coating material, and asurfactant. This concentrate is mixed with water at a ratio of about onepart concentrate to about 100 parts water to form the aqueous pigmentcomposition.

In another embodiment of the present invention, an erosion controlsystem is provided which generally comprises a flexible mattingstructured to be installed on a surface prone to erosion, the mattingincluding a core layer formed of a fiber matrix comprising plant fibersthat are effective in releasing beneficial nutrients to the slopedsurface upon decomposition of the plant fibers over a period of time.The plant fibers of the core layer preferably have a nutrient content ofat least about 0.6% potassium, about 1.25% nitrogen, and about 2.0%phosphate, based upon 100% dry matter. The fiber matrix is preferablysubstantially absent of wheat straw. Preferably, the fiber matrix corecomprises Sudan Grass (Sorgum Sudanese).

The substantial benefits of this type of erosion control product, whichdifferentiates itself from other products that are currently on themarket, are as follows:

-   -   1. Fertilization: The biodegradable plant fiber matrix products        that contain the minimum P, K, N percentages will promote and        enhance germination naturally through the decomposition of plant        biomass in the seedbed and substrate.    -   2. Turf Stage: The biodegradable plant fiber matrix material        will continue to compliment the conventional nutrients but at a        decreasing rate. The material will decompose through        decomposition of plant biomass and eventually be non-effective        after its life cycle ceases.

The enhanced Sudan Grass erosion control product is preferably comprisedof the following components:

-   Phosphorus (P): about 0.60% by weight P205 (min) on 100% dry matter    basis-   Nitrogen (N): about 1.25%-about 2.25% by weight N based upon 100%    dry matter basis-   Potassium (K) about 2.0% by weight K20 (min) and 100% dry matter    basis

The enhanced biodegradable plant fiber matrix material preferably has atleast a minimum of the above PNK components on 100% dry matter basis.Advantageously, the bionutrients within the biodegradable plant fibermatrix material will compliment conventional nonorganic nutrients, alsoknown as man made fertilizers. The decomposition of the plant biomasswithin the biodegradable plant fiber matrix material contributes to thefertility status over time. In addition, when applied to a soil surface,the present invention has been found to significantly increase thegermination ratio relative to a bare seeded soil plot.

During the turf stage, the biodegradable plant fiber matrix materialwill continue to compliment the conventional nutrients but at adecreasing rate. The material will decompose through decomposition ofplant biomass and will eventually become non-effective at the end of thedecomposition stage.

Each and every feature described herein, and each and every combinationof two or more such features is included within the scope of theinvention provided that the features included in such combination arenot mutually inconsistent.

The present invention and the objects and advantages thereof will bemore clearly understood and appreciated with respect to the followingDetailed Description, when considered in conjunction with theaccompanying Drawings and Attachment A, attached hereto and hereby madea part hereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a perspective view of an embodiment of the erosion controlsystem of the present invention, comprising erosion control mattingduring installation of the matting to a non-vegetated, sloped soilsurface to prevent soil erosion and for enhancing development ofstabilizing vegetation on the sloped surface.

FIG. 2 shows an exploded view of a portion of the matting shown in FIG.1.

FIG. 3 shows a cross sectional view of the matting shown in FIG. 1.

FIG. 4 shows a perspective view of an upper layer of the matting shownin FIG. 1.

FIG. 5 shows an exploded view of another embodiment of the presentinvention.

FIG. 6 shows an exploded view of yet another embodiment of the presentinvention.

FIG. 7 shows the embodiment of the invention shown in FIG. 1 asinstalled in an alternative application, particularly embankmentstabilization.

DETAILED DESCRIPTION OF THE INVENTION

Turning to FIG. 1, an erosion control, surface reinforcement system, inaccordance with the present invention, is shown generally at 10. Thesystem 10 is shown during installation thereof to a surface that isprone to erosion, for example a sloped, bare earth newly constructedembankment surface 11. For example, the system is being installed on thesloped surface 11 that is prone to high velocity and/or high durationhydraulic events, in order to promote the eventual growth of stabilizingvegetation on the surface 11.

Turning now to FIGS. 2 and 3, the system 10 generally comprises aflexible composite blanket, or matting 12, adapted to be temporarily orpermanently placed on or secured to the surface 11. The surface 11 maybe, for example, a newly constructed embankment, channel, a level orsloped bare earth or seeded surface. As will be appreciated by those ofskill in the art, the slope of a channel surface is typically betweenabout 3 to about 7 grade. Severe slope embankment angles are typicallydefined as 1:1 (45 degrees) or steeper.

The matting 12 generally comprises a flexible core layer 14 defining alower surface 14 a and a substantially flat upper surface 14 b. Thematting 12 further comprises an upper layer 16, secured to thesubstantially flat upper surface 14 a of the core layer 14. The corelayer 14 and the upper layer 16 define a substantially flat uppersurface of the matting 12. In addition, the core layer 14 is preferablybonded between a bottom netting layer 18 a and a top netting layer 18 b.The netting layers 18 a and 18 b are preferably stitched together,compacting the core layer 16 therebetween, for example by means of apolypropylene monofilament thread 20.

In a preferred embodiment of the present invention, the matting 12 isstructured to withstand continuous, as well as intermittent, liquidflow, for example, high velocity water flow, over the surface 13 on towhich it is placed and/or secured. The matting 12 of the presentinvention is designed to have a lower profile and more flexible thanconventional reinforcement matting while exhibiting superior, tensilestrength properties. Particularly, the matting 12, particularly an uppersurface profile thereof, has no substantial three dimensional featuressuch as grooves, troughs, cuspations, crimping, or other openstructured, three-dimensional features.

Unlike prior art erosion control blankets, the present system 10 is notdesigned to trap sediment carried in water flowing over the surfacethereof, but instead is designed to allow flowing water/particulatematter to pass freely, and with relatively low turbulence over thematting 12, while preventing soil loss from beneath the matting.

The upper layer 16 of the matting is essentially two-dimensional, and isbonded to the flat upper surface 14 a of the core layer 14. The upperlayer 16 overlies and substantially conforms to the flat surface profileof the fiber matrix layer 12.

In a preferred embodiment of the invention, the core layer 14 is formedof a flexible fiber matrix 22, preferably comprising randomly oriented,natural plant fibers, densely packed between the lower netting layer 18a and the upper netting layer 18 b. In addition, the core layer 14 has asubstantially uniform thickness, preferably at least about 0.3 inches,preferably in a range of between about 0.3 inches to about 0.5 inches,or in a range of between about 0.7 inches to about 1.0 inches. Whenconfined by the netting structure 20, the core layer 12 forms arelatively dense, uniform layer without troughs, ridges or other similarcontoured, open structured or three dimensional characteristics.

The matting 12 of the present invention preferably is constructed tohave a unit density of at least about 0.5 pounds per square yard, andmore preferably, at least about 0.7 pounds per square yard.

Advantageously, the system 10 of the present invention has been found topromote the development of a relatively warmer, more humid microclimatebeneath the matting 12, which encourages plant growth and seedgermination, in comparison to prior art erosion control blankets.

The fiber matrix 22 comprises a plurality of randomly oriented elongatedfibers or strands, for example, natural plant fibers. Other embodimentsof the invention may include synthetic fibers, and other suitable fibermaterials that are commercially available. In the presently describedhigh velocity/high duration hydraulic event matting 12 of the presentinvention, the fiber matrix 22 preferably comprises a material selectedfrom the group consisting of coconut fiber, flax fiber, choppedpolypropylene fibers and combinations thereof. Other suitable natural orsynthetic materials, for example hemp fibers, wood fibers, or plantstraw, may alternatively be used.

The top net 18 b and bottom net 18 a preferably comprise a lightweight,grid-like netting material fastened to the fiber matrix 22, for exampleby machine stitching, for example at 1.5 inch centers. Bonding of thetop net 18 b and bottom net 18 a to the fiber matrix may additionally bereinforced with deposits of a suitable adhesive.

Importantly, the flexible, two dimensional upper layer 16 is positionedto overlie and preferably closely conform to the core layer 14 to definea substantially flat upper surface of the matting being withoutsubstantial three dimensional features.

The upper layer 16 preferably comprises a relatively heavy weightpolypropylene net marketed or otherwise specified as “geo grid” asunderstood by those of skill in the art. In this particular embodiment,the upper layer 16 of the matting 12 preferably comprises a high tensilestrength, biaxial geogrid, such as shown in greater detail in FIG. 4.The geogrid is preferably “permanent” in that it is substantially notphotodegradable, and comprises, for example, PVC coated, knittedpolypropylene strands 28. Preferably, the strands 28 have a spacingdistance in a range of between about 0.2 inches to about 2.0 inches, andmore preferably in a range of between about 0.4 inches to about 1.0inches. As shown, the strands 28 define a substantially two-dimensionalgrid configuration, for example of uniform, rectangularly shapedapertures. Other suitable materials of construction may be employed inupper layer 16.

Still referring to FIG. 4, in this particular embodiment of theinvention, the upper layer 16 includes a first set of substantiallyparallel strands arranged perpendicularly across a second set ofsubstantially parallel strands. More specifically, the first set ofstrands comprises doubled strands 16 a, for example two strands arrangedrelatively close together in a side by side relationship. The second setof strands comprises twisted or helical strands 16 b having a helix-likeouter surface or substantially helical outer surface. In combination,the first set of strands 16 a and the second set of strands 16 b definea substantially planar surface, without any substantial threedimensional features or surface topography. Although a square orrectangular grid is described and shown, it should be appreciated thatother two-dimensional configurations are possible. The biaxial geogrid16 serves in part as a confinement structural layer for the fiber core12 to prevent rupture or tearing thereof, particularly during extremehydraulic activity (high velocity/high shear applications).

During high velocity water flow, for example a flow of about 20 feet persecond or greater, over an extended duration of time, for example of atleast 50 hours or more, high shear stress forces are created. Thematting 12 of the present invention has been found to have a superiorcapacity to withstand significantly greater shear stresses in comparisonto conventional matting having higher roughness values.

Flatness, or roughness, of a surface, is a measurable quality. A degreeof roughness of a surface is representable by a roughness coefficientknown as Manning's “N” value. The Manning's “N” value of the presentmatting 12 is less than about 0.44, and more preferably is about 0.026.In addition to withstanding shear stress forces, the lack of threedimensional open spacing of the matting 12 preferably is effective tolimit the amount of trapped soil and sediment which is desirable in manylong duration, high flow applications.

Assembly and manufacture of the matting 12 in accordance with thepresent invention may be accomplished using conventional equipment andmethods. For example, the fiber matrix 22 is mechanically stitch bondedbetween the netting layers, 18 a and 18 b. The layers of netting, i.e.18 a and 18 b, and fiber matrix 22 are all overlaid with the upper layer16, for example the biaxial geogrid material hereinabove described Allof the layers are then stitch bonded on 1.5 inch centers with UVstabilized polypropylene monofilament thread 20 to form thereinforcement matting 12. Alternately, or in addition, the upper layer16 can be adhered to the layers of netting 18 a and 18 b and fibermatrix 22. Any suitable, preferably water resistant, adhesive may beemployed. A number of such adhesives are well known and/or commerciallyavailable.

The matting 12 is preferably secured to the channel surface (or othersurface) by means of 8 inch (minimum size) U-shaped staples 34, shown inFIGS. 1 and 3. The staples 34 are set to intersect the machine stitchingand cross the strands 28 of the upper layer 16. Other suitable means maybe employed for fixing the matting 12 to the soil surface.Advantageously, the matting of the present invention is substantiallymore flexible than conventional erosion control blankets, allowing thematting 12 to more closely conform to the contour of the slope orembankment surface to which it is installed.

The erosion control system 10 of the present invention minimizes erosionof a channel bed and other erosion prone surfaces, particularly whensuch surfaces are subjected to continuous, high velocity flowconditions. Preferably, the matting is structured to withstand a liquidflow of between about 9.5 feet per second to about 20 feet per secondfor a duration of between about 30 minutes to a duration of about 50hours. Soil loss associated with these velocities and shear valuesdisclosed herein in accordance with the present invention, are about0.18 inches per hour as measured by industry standard accepted erodiblebed flume testing protocols and performance standards.

EXAMPLE

As a specific example, an erosion control system in accordance with thepresent invention comprises a fiber matrix core layer 14 of 100% coconutfiber and a permanent (non photodegradable) polypropylene biaxialgeogrid upper surface 16. The matting is further reinforced with anupper net 18 a and bottom net 18 b and a monofilament thread having astrength of at least about 1000 denier. The matting 12 in accordancewith this specific example has a weight of about 0.95 pounds per squareyard, a thickness of at least about 0.32 inches. Despite the Inaddition, the matting has a tensile strength of up to about 172.6 poundsper square foot, and an elongation of up to about 18.1 percent and aManning's “N” value of about 0.026. It is noted that these parameters(tensile strength, elongation) are significantly higher thanconventional erosion control blankets having a similar flexibility. Whensaid matting 12 is placed on or secured to a severely sloped,unvegetated channel surface, the matting 12 withstands continuous highvelocity flows of up about 18 feet per second for storm event durationsof up to about 50 hours or more, including peak flows of up to 20 feetper second for short durations of up to about two hours.

Turning now to FIG. 5, another embodiment of the invention is showngenerally at 110 (with like features being identified with likereference numerals increased by 100). The system 110 generally comprisesa flexible matting 112 structured to be placed on or secured to asurface prone to erosion, the matting 112 including a core layer 114formed of a fiber matrix 122 comprising randomly oriented plant fibers,wherein the plant fibers are effective in releasing effective amounts ofbeneficial nutrients to the surface upon decomposition of the plantfibers.

Preferably, the plant fiber matrix 122 has a nutrient content of atleast about 0.6% potassium, about 1.25% nitrogen, and about 2.0%phosphate, based upon 100% dry matter, and is substantially absent ofwheat straw, which is known to draw and nutrients from a soil surfaceupon decomposition of the wheat straw. Even more preferably, in thisembodiment of the invention, the fiber matrix 122 comprises SorgumSudanese, i.e. Sudan straw, or Sudan grass.

During development of the present invention, Sudan grass was found tocontain the highest amount of proteins and nutrients available to thesoil upon decomposition thereof, including nitrogen, phosphorous,potassium, magnesium, calcium and zinc, in comparison to other plantfibers such as hemp, wood, and coconut. The three components ofnitrogen, phosphorous and potassium are considered as macronutrients forsustaining plant growth and development.

Although FIG. 5 shows netting layers 18 a and 18 b and upper layer 16,it is noted that these features are not necessary and any suitablebonding means may be utilized in lieu thereof.

In an especially advantageous embodiment of the invention, shown in FIG.6, an erosion control system 210 is provided comprising a flexiblematting 212 structured to be placed on or secured to a surface prone toerosion.

The matting 212 comprises a core layer formed of a matrix 214 ofrandomly oriented rice straw fibers, preferably California rice straw.The system 210 may further comprise a reinforcement mechanism 18 aand/or 18 b, for securing the fibers of the matting in a substantiallyuniform layer.

Rice straw is available as a byproduct of the agricultural riceindustry. This embodiment of the invention advantageously provides anaturally weed free, durable matting 212 that is superior in controllingerosion relative to conventional erosion control products. It has beendiscovered that the rice straw matting of the present inventioneffectively promotes germination of seedlings and healthy growth ofvegetation. Rice straw provides a high cover factor, or aerial densityand has a high silica content. The structure of the rice straw mattingof the present invention has an aerial density that is increasedrelative to identical matting not made of rice straw. This high aerialdensity (a term that is well known and understood in the art)effectively protects the seed bed and soil from becoming displacedduring a rain event. The matting is structured to permitting asufficient amount of light to penetrate to encourage plant growthwithout drying the seed bed.

Advantageously, the system of the present invention including the ricestraw matting has a substantially higher aerial density relative to anidentical flexible matting not formed of rice straw fibers, for examplerelative to a conventional wheat straw matting system.

Although not wishing to be bound by any particular theory of operation,it is believed that that the high aerial density of the present ricestraw matting system functions to dissipate rain energy sufficiently toprotect the soil surface beneath the matting and allow plant life toflourish. The present rice straw matting of the present invention issubstantially more effective in controlling erosion on surfaces, forexample, bare sloped surfaces, during high intensity and/or longduration storm events, relative to conventional wheat straw and woodfiber matting systems.

In one embodiment of the invention, a method for controlling erosion isprovided, including the steps of applying debated rice straw fibers in asubstantially continuous, substantially even layer onto a surface proneto erosion and allowing the rice straw fibers to remain on the surfaceduring growth of seedlings and mature plants.

The present invention also provides a method for manufacturing a ricestraw blanket. The method includes the steps of pulling rice strawfibers, for example from a bulk bale of rice straw, using a blademechanism comprising a plurality of rotating blades, the rotating bladeshaving a speed of rotation effective to loosen and/or pull the ricestraw from the bale to achieve long, thin, separated rice straw fibers.These “debated” fibers are then discharged onto a conveyor surfacemoving at a speed effective to cause the fibers exiting the rotatingblade assembly to form a substantially continuous, substantially uniformfiber pile. This uniform fiber pile may then be utilized substantially“as is” as a covering for erosion prone surfaces.

Alternatively the debated rice straw may be utilized to form a ricestraw fiber blanket in accordance with the present invention. Byutilizing relatively high speed rotating blades and conveyers, thedebated rice straw fibers can be readily processed and digested byconventional blanket manufacturing material handling systems.

In one embodiment of the invention, the rice straw fiber pile ismechanically stitched or bonded to form a blanket having a substantiallyuniform thickness. The fiber pile may be stitched at specific intervals,for example, but not limited to, between about one inch and about twoinches on centers to ensure general uniformity of the blanket.Preferably, stitching is sewn with monofilament thread or twistedmultifilament thread having a minimum denier of about 1,000 denier orgreater.

In another especially advantageous embodiment of the present invention,a pigmented erosion control blanket is provided. In particular, apigmented rice straw erosion control blanket is provided, for example agreen pigmented erosion control blanket that is both visually appealingand effective as a ground covering.

A pigmented erosion control blanket in accordance with the presentinvention generally comprises a core layer comprising, preferablysubstantially entirely comprising rice straw fibers. In one embodimentof the present invention, the core layer consists essentially of ricestraw fibers. The fiber matrix preferably comprises pigmented rice strawfibers, for example, but not limited to green pigmented rice strawfibers.

In a more specific aspect of the invention, the system comprises aflexible matting useful for controlling erosion on a surface, whereinthe matting includes a core layer formed of a rice straw fiber matrixand a pigment composition deposited on the fiber matrix and effective toimpart a color to the matting. The pigment composition comprises, forexample a colorant component and a binder component, wherein the bindercomponent is effective to maintain the imparted color on the rice strawfor an increased period of time relative to a substantially identicalsystem having a substantially identical pigment composition without thebinder component.

Preferably, the pigment composition is an aqueous composition derivedfrom about one part pigment or colorant, about one part pigment binder.The binder preferably comprises a polymer coating material that iseffective to maintain the color on the rice straw fibers when the ricestraw fibers are in use as part of an erosion control system.

This embodiment of the invention is especially useful as a visuallyappealing, substantially weed free, high nutrient ground cover that aidsin preventing runoff of soil on newly developed land.

In a related aspect of the invention, a method of dyeing or pigmentingnatural fibers for use in erosion control is provided. For example, apigment composition is applied to fibers, preferably rice straw fibers,wherein the pigment composition includes a pigment component and bindercomponent effective in maintaining the pigment component on the fibersfor a substantially longer period of time relative to substantiallyidentical natural fibers that are pigmented without use of the bindercomponent. For example after the rice straw fibers have been pulled froma bulk bale as described elsewhere herein, the pigment compositioncomprising an aqueous mixture including a colorant component, apolymeric binder component, and an effective amount of a surfactant isapplied to or deposited on the fibers.

An examples of a useful, effective method of manufacturing a pigmentedrice straw blanket in accordance with the present invention is providedin the following Example. It should be appreciated that the Example isprovided for purposes of example only and is not intended to limit thescope of the present invention.

EXAMPLE Pigmentation Composition

A pigmentation solution (concentrate) is made by combining, at ambienttemperature, about one gallon of latex polymer dispersion havingtradename Pigment Green BN-Y Concentrate (Robert Koch Industries, Inc.)about one gallon of a binder component comprising a polymeric material,more specifically a polymer coating material having tradename PigmentBinder NW (Robert Koch Industries, Inc.) and a pint of a surfactantwetting agent, having the tradename Kinetic.

An aqueous pigmentation composition is made by combining, at ambienttemperature, for example a temperature of no greater than about 85° F.,in a 500 gallon tank, the pigment/binder concentrate describedhereinabove, with water at a ratio of about one part concentrate toabout 100 parts water. The aqueous composition is continuously agitatedor stirred, for example by means of a circulating pump, to preventpigment from settling to the bottom of the aqueous mixture.

Application of Pigment Composition to Rice Straw Matrix

While the pigment composition is being stirred, it is discharged fromthe tank by means of a spray nozzle onto the core layer of the matting.More particularly, the pigment composition is applied to the rice strawfibers after the stitching process, by passing the reinforced rice strawfiber matting under a low pressure spray bar which applies the aqueouscomposition onto a major surface of the matting.

This method of applying the pigment composition allows droplets of thecomposition to rapidly disperse and become effectively absorbed byand/or adhered to the rice straw fibers.

The matting is then rolled and packaged for use. Packaging of thepigmented rice straw matting of the present invention may be provided byrolling the matting and placing the rolled matting into a substantiallytubular container. Preferably, the rolled matting is placed into a“breathable” fabric container, for example a container made of a porousgeotextile material, such as a the material typically used in thepackaging of potatoes.

Any and all features described herein and combinations of such featuresare included within the scope of the present invention provided that thefeatures of any such combination are not mutually inconsistent.

While this invention has been described with respect to various specificexamples and embodiments, it is to be understood that the invention isnot limited thereto and that it can be variously practiced within thescope of the following claims.

1. An erosion control system comprising: a matting element useful forcontrolling erosion on a surface, the matting element including afibrous material comprising rice straw fibers, and a pigment compositiondeposited on at least a portion of the fibrous material; the pigmentcomposition comprising a pigment component effective to impart a colorto the rice straw fibers, and a binder component effective to maintainthe imparted color of the rice straw fibers for an increased period oftime during use of the system relative to an identical system withoutthe binder component.
 2. The system according to claim 1 wherein thefibrous material comprises substantially entirely rice straw fibers. 3.The system according to claim 1 wherein the fibrous material consistsessentially of rice straw fibers.
 4. The system of claim 1 wherein thepigment composition is derived from an aqueous composition comprisingthe pigment component, the binder component and an effective amount of asurfactant.
 5. The system of claim 1 wherein the pigment componentcomprises a latex polymer.
 6. The system of claim 1 wherein the pigmentcomponent comprises a green pigment.
 7. The system of claim 1 whereinthe binder component comprises a polymeric material.
 8. The system ofclaim 1 wherein the binder component comprises a food-grade binder. 9.The system of claim 1 further comprising a reinforcement element formaintaining structural integrity of the matting element duringinstallation of the system.
 10. The system of claim 9 wherein thereinforcement element comprises a netting element located on at leastone major surface of the fibrous material.
 11. A method of manufacturingan erosion control system, the method comprising the steps of: providinga matting element comprising rice straw fibers; and contacting at leasta portion of the matting element with an aqueous composition comprisinga pigment component effective to impart a color to the rice strawfibers, and a binder component in an amount effective to maintain theimparted color of the rice straw fibers for an increased period of timeduring use of the system relative to an identical system without thebinder component.
 12. The method of claim 11 wherein the aqueouscomposition further comprises an effective amount of a surfactant. 13.The method of claim 11 wherein the binder component comprises afood-grade binder.
 14. The method of claim 11 wherein the pigmentcomponent comprises a green pigment.
 15. The method of claim 11 whereinthe step of providing a matting element comprises pulling rice strawfibers from a bulk bale of rice straw and discharging the pulled fibersonto a conveyor mechanism.
 16. An erosion control system comprising: amatting element useful for controlling erosion on a surface, the mattingelement including a fibrous material formed substantially entirely ofrice straw fibers; wherein the matting element has at least one ofincreased aerial density, increased flexibility, increased functionallongevity, and higher silica content relative to an identical mattingelement including wheat straw fibers in place of rice straw fibers. 17.The system of claim 16 wherein the matting element includes areinforcement member located on at least one major surface of thefibrous material.
 18. The system of claim 17 wherein the fibrousmaterial consists essentially of rice straw fibers.
 19. The system ofclaim 17 wherein the reinforcement member comprises a netting member.20. The method of claim 15 wherein the step of pulling rice straw fiberscomprises utilizing a rotating blade mechanism to loosen and separaterice straw fibers prior to discharging the rice straw fibers onto theconveyor mechanism.